Infrared imaging is widely used in a variety of applications including night vision, surveillance, search and rescue, remote sensing, and preventive maintenance. Imaging devices to provide these applications are typically constructed of HgCdTe or InSb focal plane arrays. For example, quantum well infrared photodetectors (QWIPs) can detect mid- and far-infrared light, and are operable to generate an output current from the light source. Such arrays are generally complicated to manufacture and costly.
Infrared thermal imaging, which incorporates GaAs QWIPs and GaAs light emitting diodes (LEDs) via monolithic epitaxial growth integration, was disclosed by one of the applicants, H. C. Liu, in U.S. Pat. No. 5,567,955 issued Oct. 22, 1996 to the National Research Council of Canada, and in U.S. Pat. No. 6,028,323 issued Feb. 22, 2000 to the National Research Council of Canada. The former patent describes the vertical integration of a light emitting diode with a QWIP. Current from the QWIP device resulting from the impingement of far-infrared (FIR) drives the LED to emit near-infrared (NIR) photons. The NIR photons can be efficiently detected by a silicon charge coupled device (CCD), leading to a highly efficient detector. U.S. Pat. No. 6,028,323 described devices that can be used as a pixelless means of up-converting and imaging a FIR beam to a NIR beam, presented the device and system configurations that allows the input FIR energy and output NIR energy through the same side of the device. In both aforementioned patents, the vertical device integration relies on subsequent epitaxial growth of the LED layers over the QWIP layers on a same substrate.
H. C. Liu, D. Ban and H. Luo, in U.S. Pat. No. 7,079,307 issued Jul. 18, 2006 to the National Research Council of Canada describes a wavelength conversion device wherein a photodetector (PD), an avalanche multiplier (Amplifier), and an inorganic light emitting diode (LED) are integrated vertically either via subsequent epitaxial growth of the different functioning layers on a same wafer or via wafer fusion of the functioning layers which are grown on different wafers. The wavelength up-conversion from a range of 1.1-1.65 μm to below 1.0 μm (e.g., 872 nm or 923 nm) results in highly-efficient detection by a silicon charge coupled device (CCD) camera. Wafer fusion technology was employed to integrate different functioning units in a single device, which released the stringent lattice matching requirement for epitaxial growth of inorganic semiconductor materials.
Wafer fusion is an advanced processing technology that allows integrating heterogeneous semiconductor materials regardless of their lattice constant. Wafer fusion can be simply described as a direct bonding in which chemical bonds are established between two wafers/materials at their hetero-interface in the absence of an intermediate layer. It removes the limitations associated with the use of lattice-matched materials and gives a new degree of freedom for the design of novel semiconductor optoelectronic devices.
Methods for making pixelized and pixel-less QWIP-LED imaging devices are described in U.S. Pat. No. 5,567,955 and U.S. Pat. No. 6,028,323, respectively. These methods can be used for making pixelized and pixel-less up-conversion imaging devices as well. Micro-fabrication of such devices may involve mesa etching for device isolation and metal depositions for electrical contacts. Additional steps such as depositions of anti-reflection coatings and fabrication of micro-lens on device top surface may be taken for improving device performance.
The above methods and resulting devices are generally relatively complicated and costly to manufacture. There is a need for a device and method for fabrication of a device that provides an optical amplifier with desirable performance characteristics.